Combustion chamber crossover tube



Sept. 26, 1961 w. SHUTTS COMBUSTION CHAMBER CROSSOVER TUBE Filed May 15, 1958 United States Patent 3,001,366 COMBUSTION CHAMBER CROSSOVER TUBE Leroy W. Shutts, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed May 15, 1958, Ser. No. 735,555 Claims. (Cl. 6039.82)

My invention relates to combustion apparatus, particularly to such as are used in aircraft propulsion gas turbine engines, although it may be otherwise employed.

Combustion systems for gas turbine engines are of various types. One known type, to which the invention is primarily applicable, comprises a number of ducts, commonly called flame tubes or combustion liners, in which combustion is effected. These flame tubes are mounted in a combustion chamber which extends between the compressor and turbine of the engine and from which combustion air is supplied to the several flame tubes. Ordinarily, the flame tubes are disposed in a substantially parallel arrangement disposed circumferentially around the axis of the engine. Ordinarily, the combustion chamber is annular and the power output shaft of the turbine is mounted within the inner shroud of the combustion chamber.

Where a plurality of flame tubes are employed, it is the usual practice to interconnect them by tubes or sleeves commonly called crossover tubes. The principal purpose of the crossover tubes is to provide for ignition of the flame in each flame tube from the adjacent flame tube so that an ignition device is not required for each combustion space.

This invention is directed to a crossover tube and the construction of the flame tubes for reception thereof such that the application and removal of the crossover tubes and flame tubes during assembly or servicing of the engine is greatly facilitated and such that expansion or distortion of the structure due to the high temperatures prevailing is readily accommodated. These advantages are attained by a structure of remarkable simplicity and minimum weight and cost. In crossover tubes of the type mentioned, considerable wear difliculties are encountered with tubes which make mechanical contact. This invention eliminates such difficulties by providing a crossover tube made in two sections with a labyrinth interfit, thereby providing free spacing between the sections and eliminating any mechanical contact. Other objects of the invention are toimprove combustion apparatus such as is used in gas turbine engines; to facilitate assembly and servicing of such engines; to provide an improved combustion chamber and crossover tube structure; and to provide a simple, efficient, and inexpensive crossover tube. p

The preferred manner in which these objects are achieved and the advantages of the invention will beapparent to those skilled in the art from the appended description of the preferred embodiments of the invention. Referring to the drawing, FIGURE 1 is a transverse section of a portion of a gas turbine combustion apparatus, FIGURE 2 is an enlarged sectional view taken on a plane containing the axis of a crossover tube as indicated by the line 22 in FIGURE 1, and

FIGURE 3 is a modification of the construction of 'FIGURE 2.

Patented Sept. 26, 1961 rality of flame tubes or combustion liners 14. In the embodiment illustrated, there are six flame tubes, only a part of which are shown to avoid unnecessary duplication in the drawings. These flame tubes, which are generally cylindrical, are disposed with their axes parallel. They are formed with perforations to admit air for combustion from the outer chamber into the interior of the flame tubes and are fitted with fuel injection nozzles (not shown). The shrouds 10 and 12 and the flame tubes 14 are ordinarily made of heat resisting alloys such as stainless steel or Inconel. The combustion products are discharged from the flame tubes into a turbine (not shown). One or preferably two of the flame tubes are provided with fuel ignition devices :16 which may be of any conventional type. Ordinarily, the ignition device is mounted on the outer shroud 10 and projects into the flame tube 14. As illustrated, the igniter is an electrical one and includes a connector 18 for a high tension circuit. Since the structure so far described is of a sort well known to those skilled in the gas turbine engine art and the details thereof are immaterial to the invention,- further description is unnecessary.

Adjacent flame tubes 14 are interconnected by crossover tubes or sleeves 20 so that flame may be propagated from one combustion zone to another.

Referring to FIGURE 2 it will be seen that each of the adjacent portions of the flame tubes 14 are provided with suitable axially aligned opposed openings 21 and 22, the opening 22 being larger than the opening 21.

Welded to the liner 24 at the flame tube opening 21 is one end 26 of an annular or tubular section 28 of the crossover tube 20, the other end 30 extending to the opening 22. Surrounding end 26 adjacent opening 21 and extending therefrom is a sleeve 32 formed as shown to a cup-like shape having portions 36 and 38 perpendicular and parallel, respectively, to the axis of the tube section 28, with a lip flange 40 as shown for a purpose to be described.

Surrounding end 30 of crossover tube section 28 is a larger tubular section '42 having one end 44 mounted within the opening 22, with its other end 46 extending to a point adjacent the perpendicular portion 36.

Welded to the tube section 42 adjacent opening 22 and extending therefrom is a sleeve 48 having a flange 50 extending in a direction perpendicular to the axis of the crossover tube to act as a baflle for cooperation with the lipped flanged edge 40. As seen in FIGURE 2,, the righthand flame tube liner 24, and flanges 50 and 40 are approximately equally spaced axiallyfrom each other, with portions 36 and 38 of sleeve 32 having a labyrinth interfit with flange 50 and tube section 42, portion 38 overlapping both sections 42 and 28 but being laterally or radially spaced therefrom.

With this construction, the two sections 28 and 42 of the crossover tube are laterally spaced from each other without mechanical contact with the sleeves 32 and 48 having a labyrinth interfit providing an air reversal of approximately 270 degrees to restrict the flow of air to the flame tube liners. Because of this construction, any combustion chamber jacket air that enters the space between flanges 40 and 50 must follow a tortuous path as shown by the arrows 51, flowing first in a direction perpendicular to the axis of the crossover tube, then in a direction parallel to the crossover tube axis, and finally being reversed degrees to flow into the opening 22 for a total :air reversal of 270 degrees. The energy of the air flow is dissipated by the air flow striking and being turned by the tube 42, portion 36 and tube 28 to such a degree that very little air actually enters the flame tubes. This labyrinth interfit thus becomes a labyrinth-like air seal.

In the assembly of this combustion apparatus, each flame tube has secured in its adjacent opening the respec- 3 tive section of the crossover tube and its corresponding lee q P n the ls z iat i e Seal, and h tw sections are merely interfitted bgethe'r bytelescoping tube section 28 within section 4 2without any bending of the parts. The simplicity of assembly willthus be evident.

FIGURE 3 shows a modifications O'rfuie'FIG gE 2 construction wherein the sleeves have a labyrinth interfit providing an air reversal of 360 degrees. In this con struction, the two tubes sections 28 'and 42 remain th e same as previously, with the changes consistingonly the sleeve portions surrounding the tube'section's'l" seen in FIGURE 3, a sleeve 52Yis weldedto tube section 28 and the flame tube liner adjacent the opening 21 and is flared outwardly as shownto form a 'cup like section 54 similarto that of FIGURE Facing the open end of cup section 54 is the openend of an axially aligned larger cup-like section 56 formed integrally with a second sleeve 58 welded to tube section '42 and the flame tube liner 24 as shown. With this construction, cup-like portions 54 and 56 of sleeves 52 and 58 have a labyrinth in terfit with overlapping portions sound; '62 overlapping the tube sectionsl Thus, the leakage of air'from" the "com: bustion chamber jacket into the lin'ers'is reduced to a minimum since any entering a'ifniust follow a'tortu'ous path indicated by arrows 64 twicecompletely reversing the direction of air flow to'complete a 360 degree cycle. The energy or the air flow is thus lost or dissipated to such a degree in striking the portion 66 of cup-'like'section 56, tube 42, portion 68 of'cup-like section 54 and tube 28 that very little air enters ,the liner through'the opening 22. In this construction, therefore, even less air flows into the combustion liners from the combustion chamber jacket compared to that of FIGURE 2, and the labyrinth interfit of the cup-likesleeve portions and tube sections forms a labyrinth-like air seal.

From the foregoing it will be seen that the crossover tubes of this invention illustrated bythe 'embodiments of FIGURES 2 and 3 provide a labyrinth interfit connection between the flame tubes without mechanical contact permitting relative expansion or distortion of manners because of the spacing between the crossover tube sections, while preventing too great a flow of air into the liners. j

While the drawings and description describe the prefen-red embodiments of my invention, it will be clear to those skilled in the art that many modifications can be made therefrom without departing from the scope 'ofthe invention. '1

1. A combustion apparatus comprisingin combina tion, means defining acompressedairchaniberfi-a pm: rality of flame'tubes in the chamber,"a'nd crossover t'ube means interconnecting adjaceut"flame tubesfin' which each crossover tube meanscor'nprises a firsfttlbe member extending from one flame tube, a second tube member extending from an adjacent flame tube, and: parts of'tlie tube members providing an air labyrinth between the tube members, the said tube members being out of contact with each other in normal 'operation'of the combustion apparatus to accommodate thermal distortion and mini mize wear by preventing engagement of the members,-

and the air labyrinth restricting air flow into the 'cross-i 2. A combustion chamber construction comprising,

an air chamber having a plurality of flame tubes therein, anderds'sbvertuse"means interconnectingadjacent flame tubes, said crossover tube means comprising axially aligned tubular elements having overlapped end portions with a clearance therebetween, opposite end portions of said elements beingsecured each to a separate flame tube, and other means extending from each of said elements, towards each other and said overlapped ends and having portions spaced from each other and said elements to prevent contact and wear therebetween upon thermal distortion of the portions and elements, said other means together with said elements defining an air labyrinth therebetween restrictingthe flow of air into the interior of said element's.

3. A crossover tube comprising axially aligned tubular members having overlapped ends with a clearance therebetween, first sleeve means connected to one of said members and extending'towards the adjacent member, second'sleeve means secured to said adjacent member andextending towards'said one of said members'overlapping said first sleeve means and said members, the overlapping portions of said sleeve means and members having a clearance therebetweeri to prevent engagement therebetween upon thermal distortion of said members and sleeve 'means portions, 'a source of gas in communicat tion withone of said sleeve means, the overlapping sleeve means and member portions together forminga gas labyrinth for the restrictive flow of gas through said sleeve means to the interior of said members. 5 43A crossover tube as in claim 3 wherein said sleeve means include s'portions comprising a number or faceto face dished members;

"51A crossover tube comprising axially aligned tubular members having overlapped ends with a clearance therebetween, first sleeve means secured to one of said them-- bers and extending towards another of said members, second sleeve means secured to'said another of saidmembers and extending towards said" first member, baflie means "on said second sleeve means, said first sleeve means having a portion overlapping both or said tubular members; said'sleeve means portion and members and baffle means having a clearance"therebetween to prevent engagement therebetween upon thermal distortion of said members and sleeve means and baffle means, a supplyof gas, and flange means on the overlapping portion of said first sleeve means' cooperating'with said bafile means to define a gas inlet therebetween, said overlapping sleeve mean's portion and said tubular members together defining a tortuous'path for therestrictive'flow of gas from said inlet into said members.

References Cited in the file of this patent UNITED STATES PATENTS McDowall et al; Jan. 10, 1956* i. an; I 

